The working principle of photovoltaic concentration technology (CPV) is to concentrate high levels of solar radiation on a receiver with reduced size. Using an optical system of much lower cost than that of the photosensitive material itself becomes one of the major photovoltaic technologies to reduce the total cost of the generated energy.
The majority of photovoltaic concentration modules (CPV) commercially available are based on an array of small point focus concentrators. These consist of closed-type structures provided on their front outer surface with a series of lenses. These lenses focus sunlight on the active elements or cells. Adjacent to the cells the electronic adaptation components: protection diodes and wiring are placed. The space located between these components and the lenses is filled with air.
The electronic elements above mentioned are very sensitive to moisture and the exposure thereto for a long time may cause accelerated degradation, which may limit their lifetime. Although these elements are usually covered with encapsulant materials, it is very important that the recipient maintains low humidity levels.
One could think of a solution based on the seal of the module, so as to prevent the entry of air coming from the outside; however this proposal could arise some problems, since the variations of environmental temperature and pressure could induce stresses that may eventually damage the module. It is therefore necessary to provide the system with an outlet that allows the air to pass to the outside when a pressure surge is caused, and the entry thereof in the reverse process, i.e., when the internal pressure decreases. Specifically, this second case would result in the entry of moist air therein.
The modules commercially available have not satisfactorily resolved this problem and the fact that moisture can penetrate therein, creates two main problems: the progressive degradation process, mainly by oxidation, due to the moisture both of the cell and other elements, and the condensation of vapor, because the relative humidity, pressure and temperature existing within the module can eventually cause the condensation of water on the surface of the lenses, thus hindering the light pass and dramatically reducing the system performance.
To resolve this problem many solutions are provided on the state of the art, although a few ones are applied to photovoltaic concentration modules. These solutions are mainly based on inside drying the module by injecting dry air.
The air drying method can vary from one system to another. There can be found solutions that go from making use of moisture-absorbing materials to some based on absorption by cold. In the latter, at a point in the air circuit located before the inlet of the container to be dried, a drop in the temperature is caused, which makes the water vapor contained in the air to condensate. This vapor is then removed in an operation similar to air conditioners.
However, these solutions do not prevent the entry of moist air from the outside, since it is still necessary to provide the module with an outlet for the injected air to avoid pressure surges that could damage the structure itself. As previously mentioned, the inclusion of said outlet or vent valve will allow the entry of moist air from the outside. Once the moist air has penetrated and has been condensed with the cold temperatures at night, its later disposal will be translated into a high energetic effort.
The invention presented here aims to anticipate the problem, i.e. to prevent the entry of moisture into the concentration module in order to avoid problems of oxidation and condensation, and the generated energy expenditure for their elimination. In the same way it is intended to be a daily self-regenerating system and with a minimum daily energy consumption.